Electrochemical, in particular rechargeable, cells are generally known, for example from "Ullmann's Encyclopedia of Industrial Chemistry", 5th edition, Vol. A3, VCH Verlagsgesellschaft mbH, Weinheim, 1985, pages 343-397.
Among these cells, lithium batteries occupy a special position, in particular as secondary cells, owing to their high specific energy storage density.
As already known, for example from DE-A 4328785, the cathodes of such cells comprise, as a compound capable of an electrochemical reaction, mixed oxides comprising lithium ions and manganese, cobalt or nickel ions, as can be represented in the stoichiometrically simplest case by the formulae LiMn.sub.2 O.sub.4, LiCoO.sub.2 or LiNiO.sub.2.
These mixed oxides react reversibly with compounds which can incorporate lithium ions into their lattice, for example graphite, with the small lithium ions migrating from the crystal lattice and the metal ions such as manganese, cobalt or nickel ions in the latter being oxidized. This reaction can be utilized for electricity storage in an electrochemical cell by separating the compound taking up lithium ions, ie. the anode material, from the mixed oxide by means of an electrolyte through which the lithium ions migrate from the mixed oxide into the anode material.
When the cell is charged, electrons flow through an external voltage source and lithium cations flow through the electrolyte to the graphite. On utilization of the cell, the lithium cations flow through the electrolyte while the electrons flow through a load resistance from the graphite to the mixed oxide.
The electrodes of the electrochemical cells comprise a support, usually a metal, and, applied thereto, a binder layer in which the anode material, usually graphite, or the mixed oxide as cathode material are finely distributed. To coat the support, a suspension of the electrode materials and a solution of the binder are applied to the support, after which the solvent is evaporated.
To make possible output or input of power to the electrodes via contact points, the support may at these contact points have no coating which is known to have a high electrical resistance.
This has been achieved hitherto by printing the coating onto the support in the desired geometry and subsequently stamping the electrode including the contact point from the support material.
This process does not lead to satisfactory products, since the uniformity of the coating thickeners required for the operation of effective batteries cannot be achieved. Furthermore, this process has to be completely converted on each change of the electrode size.
To eliminate these disadvantages it has been proposed to completely coat the support, to stamp out the electrode including the contact point and subsequently to again remove the coating in the region of the contact point.
This process is technically very complicated and runs the risk of damaging the support material when removing the coating.